The machine for figuring out what’s going on inside a living brain—well, it doesn’t look much fun for the mouse under the business end. At the Allen Institute for Brain Science, in Seattle, researchers first peel away a piece of a mouse’s skull—a lot of mice, actually—and replace it with a little window with holes in it. Then they lock the mouse into a frame that bolts onto its head.
The actual brain-scanning part is called a Neuropixels probe, a 10-mm long needle made with the same technology as computer chips. Six of them sit on a cartridge that descends on a robot arm through the holes in the skull window and into the mouse’s brain. Each needle is studded with almost 1,000 sites that can record neural activity, the electrical spikes of neurons talking to each other. The Allen researchers plunge those into the deepest regions of the visual cortex.
Then they show things to that mouse and use the Neuropixels to see what the brain does in response. What kind of stuff? A grid. A black-and-white grating. Another grating, but this time moving slowly. The sort of visual stimuli that every kind of mammal’s brain responds to. Also: pictures of the natural world, animals and more. They also showed the mice two clips from the long, single-take opening scene of the Orson Welles movie Touch of Evil, over and over again. All the while, the Neuropixels collected data from hundreds, perhaps thousands, of neurons localized with a brain-mapping standard the institute came up with.
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It’s not so easy to peer inside a mouse’s head.
Photograph: Allen Institute
On Monday, the Allen Institute gathered up all 70 terabytes of raw neuroelectrical data, sorted it into 850 gigabytes of more useful information, and gave it—plus maps and new visual imaging of the brain at work—away. That’s the point. To provide the people studying brains, computers trying to simulate brains, and brain-computer interfaces with some actual numbers to work with. “For the last 50 years, people collected data from just 30 neurons, 40 neurons,” says Christof Koch, chief scientist at the Allen Institute. “It’s very different if you have 2,000, or 50,000, or 100,000 like we have.”
Koch says this dataset shows action from connected regions across the brain—maybe 1,000 neurons simultaneously from 10 different areas along the length of the probe, from one visual area to another, or from visual areas to regions where higher-order processing happens. That’s orders of magnitude more neurons than what most researchers can observe. “It’s really going to dramatically change how neurophysiology is done.”
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